text: The identification of a factor as limiting is possible only in distinction to one or more other factors that are non-limiting. Disciplines differ in their use of the term as to whether they allow the simultaneous existence of more than one limiting factor which (may then be called "co-limiting"), but they all require the existence of at least one non-limiting factor when the terms are used.  There are several different possible scenarios of limitation when more than one factor is present.  The first scenario, called single limitation occurs when only one factor, the one with maximum demand, limits the System.  Serial co-limitation is when one factor has no direct limiting effects on the system, but must be present to increase the limitation of a second factor. A third scenario, independent limitation, occurs when two factors both have limiting effects on the system but work through different mechanisms.  Another scenario, synergistic limitation, occurs when both factors contribute to the same limitation mechanism, but in different ways.
  In 1905 Frederick Blackman articulated the role of limiting factors as follows: "When a process is conditioned as to its rapidity by several separate factors the rate of the process is limited by the pace of the slowest factor." In terms of the magnitude of a function, he wrote, "When the magnitude of a function is limited by one of a set of possible factors, increase of that factor, and of that one alone, will be found to bring about an increase of the magnitude of the function."